People rely on health and hygiene products to make their lives easier.
Health and hygiene products, such as various disposable absorbent articles (e.g., adult incontinence articles and diapers), are generally manufactured by combining several components. These components may include, for example, a liquid-permeable topsheet; a liquid-impermeable backsheet attached to the topsheet; and an absorbent core located between the topsheet and the backsheet. When the disposable article is worn, the liquid-permeable topsheet is positioned next to the body of the wearer. The topsheet allows passage of bodily fluids into the absorbent core. The liquid-impermeable backsheet helps prevent leakage of fluids held in the absorbent core. The absorbent core generally is designed to have desirable physical properties, e.g. a high absorbent capacity and high absorption rate, so that bodily fluids can be transported from the skin of the wearer into the disposable absorbent article.
Frequently one or more components of a health-and-hygiene article are adhesively bonded together. For example, adhesives have been used to bond individual layers of an absorbent article, such as the topsheet (also known as, for example, the body-side liner) and backsheet (also known as, for example, the outer cover), together. Adhesive has also been used to bond discrete pieces, such as fasteners and leg elastics, to the article. In many cases, the bonding together of components forms a laminated structure in which adhesive is sandwiched between materials (such as layers of polymer film and/or layers of woven or nonwoven fabrics) that make up the components being bonded together. In some cases elastic strand, or some other elastomeric material, is attached to and/or sandwiched between other components.
In many instances, a hot-melt adhesive, i.e. a formulation that is heated to substantially liquefy the formulation prior to application to one or both materials when making a laminate, is used in making a laminated structure. While such formulations generally work, they can be improved upon. For example, in making some elastomeric composites, the add-on rate of the adhesive may be relatively high, resulting in a relatively costly, and somewhat rough or stiff, composite. E.g., the production of an elastomeric composite comprising one or more elastic strands sandwiched between, and adhesively attached to, nonwoven substrates (or facings) may require significant amounts of adhesive to ensure that the strands are satisfactorily attached to the nonwoven facings, thereby giving the composite its elastomeric qualities. At every location where a strand is adhesively attached to one or both facings, the composite is stiffer, because the combination of the strand, nonwoven facing, and adhesive is thicker and stiffer than either the strand alone or the nonwoven facing alone. If the composite comprises many such attachment locations, then the resulting composite may be stiff, rough, and/or perceived by users of the composite as not being soft. Furthermore, as the number of attachment locations is increased, the elastic qualities of the elastomeric composite may decrease, because more and more of the strand is attached to the nonwoven facings, with less and less of the strand remaining unattached. As less and less of the strand remains free and unattached—and therefore readily able to stretch or retract—the resulting composite is less stretchable and/or retractable. Conversely, as more and more of the strand remains free and unattached, the resulting composite is more stretchable and/or retractable.
The problem of achieving the desired balance between the integrity of an elastomeric laminate and effecting desired properties of softness/flexibility and elasticity may be exacerbated at the higher line speeds typically associated with commercial equipment (e.g., the equipment used to make a disposable absorbent article such as a diaper, which may operate at speeds, for example, of at least 300 feet per minute; suitably 500 feet per minute, particularly 750 feet per minute). As the line speed of the equipment increases, it typically becomes more and more difficult to intermittently attach an elastomeric material, such as elastic strand, to a substrate. For example, if the laminate is being made by attaching elastic strand to a substrate using a hot-melt adhesive applied through a nozzle, then intermittent bonding might be achieved by rapidly pulsing the adhesive (i.e., applying it in a discontinuous fashion). But at higher and higher line speeds, the pulsing of adhesive at higher and higher frequencies may be mechanically difficult. I.e., it may be difficult to produce the desired pattern of discrete bonding points between the elastic material and the substrate.
What is needed is a composite (e.g., an elastomeric composite), and method of making such a composite, that provides for one or more performance characteristics that are comparable to, or better than, one or more of the same performance characteristics (e.g., bond strength) of a conventional composite, while at the same time having improved softness characteristics. E.g., what is needed is a composite comprising elastomeric materials, such as elastomeric strands, attached to one or more substrates such that the composite has sufficient integrity, elasticity, and softness for use in a product.